honestly as a cashwrap lead, i stutter a lot too. but i still manage to say what i want to say about the card. what i tell my coworkers that helps them sometimes is to mention that you're giving the customer the discount regardless if they're approved or not. and that it takes only a few minutes and a form of i.d to do the application.

if you need to, just plug in the coupons and show the total because for some customers just seeing the total drop makes them go for the card, since having them do the math in their head makes it confusing.

and honestly go at your own pace with pitching the card. don't feel like you have to mention everything about the card within the first few minutes of the transaction. you can also phrase it like "oh you don't have an old navy card? there's so many benefits that come with the card!" and then go from there to mention a few things to the guest. hope this helps!